I have designed a rectifier and regulator for RFID Tag. Both are working fine when they are simulated independently.
When I gave 500mV as input to 4-stage rectifier, I got 1V output for open load ckt condition.

Now, I have connected rectifier to regulator. Rectifier output is 500mV. What may be the reason? Because of the load, current decreases. That is fair. But why voltage is decreasing? Any clue. When regulator has run independently, it consumes 836nW of power. I am in desperate need of help. Pls help me.